356 ANATOMY FOR NURSES [Chap. XVIIl 



sibie, as in infants, an increase in fats serves the same purpose as 

 exercise in a healthy aihilt. 



Heat regulation by clothing. — By clothing we can aid the func- 

 tions of the skin and the maintenance of heat ; though, of course, 

 clothes are not in themselves sources of heat. The object of 

 clothing is, in winter, to prevent conduction, radiation, and evapo- 

 ration of heat from the skin, and in summer to promote it. In 

 considering the heat value of clothing the important properties are : 

 (1) whether it is loosely or tightly woven, (2) its thickness, and 

 (3) its color. 



(1) Materials that are loosely woven will be warmer than those 

 that are tightly woven, because the meshes in a loosely woven 

 material are capable of holding air, which is a poor conductor 

 of heat, and thus prevents radiation. 



(2) Thick material does not allow cold air to penetrate to the 

 skin. 



(3) Dark colored materials absorb heat to some extent, hence 

 they are warmer than light colored textiles. Thick, porous ma- 

 terials are used to keep the body warm. Wool has an additional 

 advantage, as evaporation takes place more slowly from it than 

 from linen, cotton, or silk. Thin and very porous materials help 

 to keep the body cool, because they allow the air to penetrate to 

 the skin, and thus assist the evaporation of sweat. 



Heat regulation by baths. Hot baths. — The primary effect 

 of a hot bath is to prevent radiation of heat from the surface of 

 the body, and some increase in temperature may result. If the 

 bath is not continued for too long a time, this effect is counteracted 

 by the increased perspiration that follows. 



Cold baths. — The primary effect of a cold bath is similar to the 

 effect of cold air. The cold contracts the arterioles of the skin, 

 drives the blood to the interior, and increases oxidation. If the 

 bath is a short one and is followed by friction, the reaction is for 

 the arterioles to dilate, the heated blood is sent to the surface, the 

 circulation is quickened, and there is a consequent loss of heat. 

 In health the gain in heat is usually balanced by the loss of heat, 

 and the purpose of a cold bath is to exercise the arterioles and 

 stimulate the circulation. If the bath is continued for some time, 

 the temperature of the skin, and of the muscles lying beneath, is 

 reduced, and either the heat-producing processes may be checked 



